In a centrifuge, generally, a sample stored in a tube or a bottle is housed within a rotor, and separation and refinement or the like of the sample rotating together with the rotor are performed by the rotor being rotated at a high speed by a driving device such as a motor in a rotor chamber (rotation chamber) sealed by a door.
A rotation speed of the rotor differs depending on usage, and a family of products having a wide range of rotation speeds from one having a comparative low-speed where the maximum rotation speed is about several thousands of rpm (revolutions per minute) to one having a high-speed of 150,000 rpm has been generally provided. Among them, a centrifuge having a rotor and the rotor's rotation speed substantially exceeding 40,000 rpm (hereinafter, referred to as a “ultracentrifuge”) is provided with a vacuum pump which depressurizes a rotor chamber to suppress a temperature rise of the rotor and a sample in the rotor due to friction heat between air in the rotor chamber and the rotor. In this way, in the ultracentrifuge, since an operation thereof is performed by depressurizing the rotor chamber, the friction with air becomes small.
In Patent Document 1 shown in the following, disclosed is a technology of achieving shortening of a cooling time of the rotor by carrying out rotation at a low speed until the rotor temperature reaches a desired temperature, and carrying out acceleration up to a configured rotation speed after reaching the desired temperature.
Under a depressurized environment, since heat exchange based on radiation becomes dominant rather than heat exchange based on convection, cooling of a rotor and a sample in the rotor takes time as compared with a state under a non-depressurized environment (for example, under an atmospheric pressure environment). From this, in the case of using a sample which must be handled at a low temperature, the rotor and sample are cooled in a coolerator or the like in advance, or are cooled within the centrifuge for a long time. In this manner, there is a trade-off relation between friction heat reduction based on depressurizing in the rotor chamber and shortening of the cooling time of the rotor and a sample in the rotor in the rotor chamber. Even if the rotor rotates at a low speed until the temperature of the rotor reaches a desired temperature as shown in Patent Document 1, a cooling time can be shortened little under the depressurized environment where the heat exchange based on radiation is dominant, and a long time is required for a rotor temperature to reach the desired temperature.
On the other hand, although the cooling of the rotor and a sample in the rotor becomes quicker due to the air convection if the inside of the rotor chamber is cooled in a state of an atmospheric pressure, the inside of the rotor chamber dews or freezes and thus it takes a long time for the depressurization. That is, if there is dew water or ice, the dew water or ice must be evaporated when depressurizing the inside of the rotor chamber with a vacuum pump operated. Therefore, there has been a problem that it takes an excessive time until a degree of vacuum in the rotor chamber reaches high vacuum, and a long time is required until the rotor is rotated at a high speed.